1. Field of the Invention
The present invention relates to a document conveying device, an image reading device, and an image forming apparatus.
2. Description of the Related Art
Previously known are image forming apparatuses including an image reading device provided with a document conveying device that feeds documents one by one from a document table on which the documents, i.e., sheets, are stacked, to a read position at which a document image is read by an image reading unit.
A document conveying device disclosed in Japanese Patent No. 3694012 includes a driving shaft that is a rotating shaft member to be coupled to a driving source provided on a device body, and a rotary driving force from the driving source is transmitted to the driving shaft. The driving shaft is attached with a feeding roller holder that is one of rotating members rotatable with respect to the driving shaft, and on the inner side of the feeding roller holder, a feeding roller and a separating belt are arranged. The feeding roller is coupled to the driving shaft via driving force transmitting members such as gears and a belt, and is held to the feeding roller holder together with the driving force transmitting members. The separating belt is stretched between a driving roller attached to the driving shaft and a driven roller that follows to rotate with the surface movement of the separating belt. On both sides of the driving shaft in the axis direction intervening the feeding roller holder, a pair of guide plates that is one of the rotating members rotatable with respect to the driving shaft is attached. The guide plates constitute a part of a document feed path on which a plurality of conveying rollers are provided, and serve to guide a document conveyed by the conveying rollers towards a read position set on the device body.
The feeding roller contacts an upper surface of the topmost sheet of a stack of sheets placed on a document table and drives to rotate so as to exert a conveying force to the single sheet of document. The separating belt separates the topmost sheet, which is exerted with the conveying force and is fed by the feeding roller, from other sheets that are overlapping the topmost sheet and are conveyed together with the topmost sheet. The topmost sheet thus separated from the other sheets is conveyed towards the read position by the conveying rollers while being guided by the guide plates.
Furthermore, replacement work and maintenance work are performed as dirt accumulates and wear occurs on the feeding roller and the separating belt in use over time. In the document conveying device described in Japanese Patent No. 3694012, the driving shaft is made detachable from the device body. Moreover, the feeding roller holder combined with the feeding roller and others is made detachable from the driving shaft. Accordingly, removing the driving shaft from the device body and further removing the feeding roller holder from the driving shaft allow workability in replacement work and maintenance work of the feeding roller and the separating belt to be substantially improved.
When attaching the driving shaft to the device body after finishing the replacement work or the maintenance work, there may be a situation in which the positions of the guide plates are inverted with reference to the position of the feeding roller holder. In this case, the positions of the guide plates are in a different position from a normal position in which the conveyance of the sheet can be guided. When the driving shaft is attached to the device body as it stands, the guide plates may be damaged or poor conveyance may result.
The rotating members rotatably attached to the driving shaft are not limited to the guide plates. For example, there may be a situation in which a lifting member rotatably attached to the driving shaft and to raise and lower the feeding roller holder in connection with the rotation of the lifting member is used as a lifting unit to raise and lower the feeding roller holder so as to make the feeding roller contact with and separate from a stack of sheets stacked on the document table. In this case, when the driving shaft is attached to the device body while the position of the lifting member is different from a normal position in which the feeding roller holder can be raised and lowered, the lifting member may be damaged or a failure in document feeding by the feeding roller may result as the feeding roller holder cannot be raised and lowered.
Therefore, when attaching the driving shaft to the device body, it is necessary to prevent the occurrence of wrong assembly in which the rotating members such as the guide plates and the lifting member rotatably attached to the driving shaft are assembled to the device body in a position different from a given predetermined position.
Therefore, there is a need to provide a document conveying device that can prevent the occurrence of wrong assembly in which rotating members rotatably attached to a rotating shaft member is wrongly assembled to a device body, and an image reading device and an image forming apparatus provided with the document conveying device.